The present invention relates to a parcel (i.e., packaging arrangement) of at least one pair of stacks of units of goods surrounded by a self-clamping sling. The invention also comprises a prefabricated sling for forming such parcels. The invention further comprises a method of forming such parcels comprising a self-clamping load sling and an apparatus for performing the method.
Transport and storage of units of goods or bags are, to a great extent, performed by stacking the goods on pallets which usually are covered and protected/secured by foliar plastic sheet. This is a rather expensive procedure, mainly because of the cost of the pallets, including the cost of reusing, refurbishing, repairing and transporting the pallets.
Proposals for overcoming these problems by using slings instead of pallets are known. From WO 88/06554 there is known a process and machine for making up a parcel of bags from adjacent stacks of bags and two straps forming a closed loop. The straps encircle the stacks of bags, transversally with respect to the bags, and the lower part of the straps extends upwards between the stacks of bags to form a central suspension loop for lifting the parcel. The application of a pair of straps complicates the handling of such parcels because it requires two suspension loops to be hooked onto lifting devices like hooks or truck forks. The stability of such parcels is questionable and the narrow width of the straps will, for many types of goods, damage the bags during handling. The openings in the straps through which the suspension loops protrude are complicated, and it requires strict control to ensure that the strap ends are kept together during handling.
A similar arrangement for handling stacks of bags is described in GB patent specification No. 1.409.243. In this case, two sets of loop-formed straps surround the bags, but the common suspension loop for lifting the parcel of bags is threaded through a ring to which the strap ends are secured. This arrangement is even more complicated than that described above. The disadvantages with regard to stability and possible damage to the bags are similar to those described with respect to WO 88/06544.
The objective of the invention is to provide a safe and economic way of handling units of goods or bags that would not require pallets and which did not have the disadvantages related to known sling devices for handling bags.
Another objective is to develop a method and apparatus for placing the bags in a lifting and storage device that meets the requirements with regard to safety and stability for parcels (packaging arrangements) of stacks of bags to be handled by commonly applied lifting devices.
A further objective is to obtain an improvement in the sling device itself by providing a more efficient way of forming the sling.
When the inventors started looking for new ways of avoiding the application of pallets for transporting/storing bags, the concept of self-clamping slings seemed promising in spite of the disadvantages and shortcomings of the known solutions within this concept. It was therefore decided to try to develop improved sling type lifting devices for bags. The problems related to the application of narrow straps were first investigated. Substitution of such straps with a wide belt or cloth, for instance, one having a width substantially equal to the length of the bags, was then proposed. However, such a solution seemed to result in several new problems. First of all was the problem of joining the ends of such a belt to a joint that would be strong enough to meet the requirements with regard to lifting strength through the lifetime of the belt, i.e., through several lifting operations. Another problem was to gather together a wide belt to form a suspension loop for lifting the stacks of bags. Then an opening had to be made in the belt for the lifting loop without reducing the lifting strength of the looped belt. The latter problem proved to be very simple to solve by simply slitting an opening in the belt in the area just above the two self-clamping stacks of bags.
To make a strong joint for the belt ends required selection of the right material for the belt and the proper way of forming the joint. The belt could be made from any cloth material having the required strength, and such material could be polypropylene, polyethylene, jute and even paper. Sewing, application of various types of glue, hot melt etc. were considered. The belt ends could also be joined by a clamping device consisting of a female and male member. In this way, the belt ends are folded around the respective male and female members until they are locked together. Weldable materials can also be joined by welding. The final solution to this problem would also have to incorporate a solution taking into consideration the method of forming the looped belt with bags stacked therein. Accordingly, a new method and device for placing the bags in such a looped belt had to be developed. In order to arrive at an economically acceptable solution, it was decided that the problem of designing a device for stacking bags into the belt had to be developed simultaneously with solving the problems of obtaining a secure and permanent joint between the belt ends.
The method of forming parcels of self-clamping load sling of stacks of units of goods or bags according to the invention, comprises using a sling in the form of a belt having a width substantially equal to the transverse width of the stacks. The sling is formed into a closed loop comprising a suspension loop for lifting the parcel. A predefined length of the belt is first formed from a belt supply, and then at least two stacks of units of goods are placed on the belt such that the belt surrounds the stacks and extends upwards between the stacks to form a tapered central suspension loop. An opening is provided in the belt for pulling the loop through and then forming the loop and thus the lifting means or eye. The two ends of the belt are joined together to form a closed loop.
A modification according to the method of the present invention is shown in FIGS. 7-11. The main features of this method relate to formation of the central suspension loop and placement of a sleeve around the loop.
A special way of forming the sling was developed. This required treating the belt material, or at least those parts which should be joined together, by irradiation or corona discharge. The adherence of the glue or hotmelt to the belt material was then substantially strengthened. This solution to the problem proved to provide belt joints that could endure the strain the parcels were exposed to during lifting. The joints were strong enough even during lifting at relatively high temperatures. It was further found that when a retaining agent such as a sleeve was applied around the suspension loop, the sleeve material could be made from corona treated base material and glue, or hotmelt could be applied for joining the material to a sleeve. Similar material, such as woven polypropylene fabric, is usually applied for, for instance, making flexible intermediate bulk containers, and instead of using seems for joining the various parts of the material, it can be treated with corona discharge and glue and hotmelt can be applied to the joints.
An alternative method of forming the parcels of units of goods comprises using a predefined length of a belt having a width substantially equal to the width of the stacks of units of goods. The belt is formed into a closed loop by placing the belt over four rods being transverse to the belt, forming the central suspension loop, and then placing the belt around another set of four rods and joining the two belt ends into a closed sling. An opening in the upper part of the belt is provided for pulling the suspension loop through and gathering the loop to form a lifting eye. The units of goods are stacked into the belt subsequent to formation of the closed sling.
The apparatus for forming a parcel of at least two stacks of units of goods surrounded by a sling comprises a supply of loop material in the form of a belt or cloth which during production of the parcel of stacks will pass over two pair of rods spaced apart. Each such pair of rods has a vertically displaceable rod placed between the rods for providing, together with a vertically movable plate with two rods secured thereto, the predefined length of the belt. The outer end of the belt is fastened in a clamping device during the whole stacking operation.
At the end of the operation, the clamping device can be moved horizontally above the stack of bags in order to place the outer end of the belt in position for being joined to the other end of the belt. The apparatus further comprises a device for supplying units of goods to be stacked in the sling. Any suitable device for placing the units or bags on the belt and subsequently on the previous bag can be applied. The device also comprises at least two roll assemblies on which the predefined belt rests during the stacking operation. These roll assemblies can be moved vertically.
The parcel according to the invention comprises at least one pair of stacks of units of goods surrounded by a loop-formed sling comprising a tapered central suspension loop extending upwards between the stacks of units of goods. The sling is in the form of a closed loop of a belt having a width substantially equal to the transverse width of the stacks, and the central loop is gathered together to form a lifting eye, which optionally can be reinforced by a sleeve of suitable material. The belt ends overlap, preferably across their total width, and are permanently secured together by sewing, gluing, hot melt etc.
A corresponding parcel can be made by simply placing a pre-defined length of a belt over eight rods and joining the two ends of the belt on top of the stacks of units of goods or bags. The bags can be loaded into the belt manually.